In the conventional design of the vehicle lamp, the demand and regulation for high beam and low beam are different. High beam requires concentrated light to achieve the purpose of long-distance illumination, but low beam requires diffused light to provide a wide viewing field in the close range. Accordingly, the designs of high beam and low beam are usually separated in the concept for designing the vehicle lamp. That is to say, each of high beam and low beam has specially adapted lamp cup. For instance, Taiwan Patent Publication No. M353845 discloses an headlight structure for driving illumination, in which the automobile light structure has the function of switching between high and low beam modes by individually independent high and low beam modules.
Generally, light emitting modules of the conventional vehicle lamp can be classified into halogen lamp and high intensity discharge (HID) lamp. The arc lengths of halogen lamp and HID lamp are about 5.6 mm and about 4.3 mm, respectively; and the projector ellipsoid system (PES) is usually selected to be the light converging system. Since the major light emitting type of HID lamp is focus on two electrodes, the light of high beam can be distributed from the position nearing the light point with high light intensity, and the light of low beam can be distributed from the position far away from the arc with strong light intensity. However, the headlamp with the combined system of high and low beam is difficult to be designed under the single lens structure because that the light emitting type of light-emitting diode (LED) is uniform surface light source without high light intensity area. If the combined system of high and low beam is designed under the conventional single lens structure, the overall vehicle lamp will have large volume and the light emission intensity of the vehicle lamp will reach at most the threshold value of the correlated rule.
As a result, there is an important issue to overcome the aforementioned defects for a person of ordinary skill in the art, by performing a switchable function of high and low beams under LED light source and the single lens structure.